Infectious diseases and the increasing threat of worldwide pandemics have underscored the importance of antibiotics and hygiene. Microbial infection is also one of the most serious concerns for many commercial applications, such as medical devices and hospital surfaces, textiles, food packaging, children's toys, electrical appliances, and dental surgery equipment. Intensive efforts have been devoted to create self-disinfecting and microbicide surfaces, mainly achieved by coating microbicides onto surfaces to biochemically reduce the infectivity of microbes. However, critical challenges still remain at this point such as growing drug resistance to the microbicide agents, low microbial killing efficacy and poor long-term stability of the coated surfaces.
It was recently disclosed that a biological strategy relying on a physical mechanism of action rather than a biochemical mechanism of action provided a promising solution to bacterial growth. In this disclosure, it was discovered that cicada wing surfaces are covered with dense patterns of nanoscale pillar structures, which are cylindrical and have rounded ends, and prevent bacterial growth by rupturing adhered microbial cells. It was also proven that a purely physical interaction between synthetic nanopatterns, such as black silicon surfaces, and cells also results in cell deformation and massive lysis without the need for additional external chemicals or mechanical means to aid in microbial killing. This discovery of a physical mechanism of action opens up a great opportunity for the development of innovative microbicide surface technologies which are clean and safe, require no external chemicals and have no microbial resistance issues. However, there are no existing technologies that can create such cell-destructive surfaces in an efficient and simple way.
As mentioned above, nanostructures on surfaces of black silicon and TiO2 have demonstrated microbicide properties. These surface nano-patterns were generated by a top-down approach on specific materials, which becomes very challenging when the patterns go down to the nanometer scale. Accordingly, these surfaces tend to be prohibitively expensive and the method of synthesis is limited to certain types of materials.
On the other hand, metal organic frameworks (MOFs) construct their defined nano-patterns via a bottom-up (self-assembly) approach with metal species and polyfunctional organic linkers. This approach has been used for growing MOF membranes or films on the surfaces of various substrates. Therefore, the quest for integrating MOFs into substrate-based applications like sensing, separation and catalysis has attracted increasing attention in the past decade. This interest is correlated to the unique properties of MOFs, such as the mild reaction conditions for synthesis and their proven chemical and thermal stability. However, the bottom-up approach has not been applied to the preparation of biomimicry surfaces that demonstrate microbicide properties.
There is therefore a need to provide a surface or coating demonstrating microbicide properties that overcomes, or at least ameliorates, one or more of the disadvantages described above.
There is also a need to provide a general and scalable method of making patterned surfaces with high microbicide activity.